Let's look at a pond from a different perspective..... thinking about the 3 zones that are in play w

Published: Sat, 21 Sep 2013Updated: Sat, 21 Sep 2013Mark Lawson

While accounting for only 3% of the Earth's surface, lakes and ponds are vital habitats, and provide essential resources for a wide range of species, including humans. Like zones for plant hardiness there is also 3 zones for life at different levels in a pond or lakes. These zones support different life forms for each zone.

While accounting for only 3% of the Earth's surface, lakes and ponds are vital habitats, and provide essential resources for a wide range of species, including humans. Like zones for plant hardiness there is also 3 zones for life at different levels in a pond or lakes. These zones support different life forms for each zone. We have all seen it but maybe never thought about looking at it with this perspective. We will break down each zone as:

Littoral Zone

Limnetic Zone

Profundal Zone

The Littoral zone is the area closest to the shore. This zone is the warmest since it is shallow and can absorb more of the Sun’s heat. It sustains a fairly diverse community, which can include several species of algae (like diatoms), rooted and floating aquatic plants, grazing snails, clams, insects, crustaceans, fishes, and amphibians. In the case of the insects, such as dragonflies and midges, only the egg and larvae stages are found in this zone. The vegetation and animals living in the littoral zone are food for other creatures such as turtles, snakes, and ducks.

The Limnetic zone is the layer of open water where photosynthesis can occur. The near-surface open water surrounded by the littoral zone is the Limnetic zone. The limnetic zone is well-lighted (like the littoral zone) and is dominated by plankton, both phytoplankton and zooplankton. Plankton are small organisms that play a crucial role in the food chain. Without aquatic plankton, there would be few living organisms in the world, and certainly no humans. A variety of freshwater fish also occupy this zone.

Very deep lakes have an area known as the Profundal zone where light does not reach. This zone is inhabited by organisms that are either attached to or crawl along the sediments at the bottom of the lake. The sediments support a large population of bacteria and fungi. The decomposers break down the organic matter and release inorganic nutrients. Most of our ponds are not deep enough to have the Profundal zone, but none the less we do have the same decomposing break down going on but at a lesser depth. Just as an organism has a particular home, or habitat, it also has a certain job to perform in the community. All organisms may be classified into one of three categories. Organisms containing chlorophyll and therefore manufacturing their own food by photosynthesis are known as producers. Organisms that feed directly upon the producers and upon organisms are known as consumers. These organisms are unable to manufacture their own food. Bacteria and fungi that react upon dead matter and free useful compounds, elements, and minerals so that the producers may utilize them once again are called reducers.

Photo supplied by "The Kansas State Emporia State University"

The picture above gives a better perspective of the different levels were discussing. There is one other level to look at Benthic zone. This is an interesting level as it can be found at shallower depths, there are many more photosynthetic microbes. At greater depths, microbes do not have access to light and heat and must rely on detritus for energy. The organisms in the Benthic zone are classified into those which dwell on the surface and those which burrow into the pond floor. We would find this more in mud ponds then in concrete or liner substrates. But none the less does occur in most ponds that may have detritus build up or some form of gravel or rock lining bottom. Benthic microorganisms are almost exclusively microalgae and bacteria, but other others include: ciliates, amoebae, and flagellates. In general, most organisms there are detritivores and scavengers because of the abundance of dead or decaying organic matter. In addition to these heterotrophs, there are chemoautotrophs present that use the substrate to make biomass. There are also photoautotrophs present at shallower depths where sunlight is abundant. The impacts of benthic microorganisms spread, much like the impacts of all other microbes, across the community as a whole. They provide essential energy and nutrients at the lower levels of the food chain and are imperative to the success of other forms of life. So next time your out feeding your fish and trimming plants or just enjoying your Eco-system take minute and see if you can identify the Zones in your pond. Until next time............Happy Ponding- Koiman

Glossary

Aphotic zone: Depth of the water where there is little to no sunlight for photosynthesis to occur

Benthic zone: The sediment layer of lentic systems Epilimnion: The top layer of water in a thermally stratified water body

Eutrophic: A lentic system with high nutrient concentrations and high plant growth

Food web: Feeding relationships among organisms within an ecosystem or community

Hydroperiod: The length of time that a lentic system contains standing water

Hypolimnion: The bottom layer of water in a thermally stratified water body

Hysteresis: A system that exhibits path dependence such that the output depends in part on the internal state of system and not only on its input

Laurentian Great Lakes: The five largest North American lakes formed by the retreat of the Laurentide ice sheet about 10,000 years ago Limnetic zone: The open-water habitat of lentic systems beyond the littoral zone

Limnology: The study of the structural and functional interrelationships of organisms of inland waters as they are affected by their dynamic physical, chemical, and biotic environments

Littoral zone: The near-shore habitat of lentic systems

Macrophyte: An aquatic plant that grows in or near water and is either emergent, submergent, or floating Oligotrophic: A lentic system with low nutrient concentrations and low plant growth

Oxbow lake: Water body formed when a wide meander from a river system is cut off

Periphyton: Complex mixture of algae, cyanobacteria, heterotrophic microbes, and detritus that are attached to submerged surfaces in aquatic environments

Photic zone: Depth of the water that is exposed to sufficient sunlight for photosynthesis to occur

Phytoplankton: Photosynthesizing microscopic organisms that are suspended in the photic zone of the water column